1. Field of the Invention
The present invention relates generally to an improved scored rupture disk manufacturing method, and more particularly, but not by way of limitation, to methods of manufacturing scored rupture disks of both conventional and reverse buckling rupture types whereby the scores are formed in the disks by corrosion.
2. Description of the Prior Art
A variety of safety pressure relief devices of the rupture disk type have been developed and used. Generally, these devices include a fluid pressure rupturable member or disk supported between a pair of supporting members which are in turn connected to a relief connection in a vessel or system containing fluid pressure. When the pressure within the vessel or system exceeds the design rupture pressure of the rupture disk, rupture occurs causing excess fluid pressure to be relieved from the vessel or system.
Heretofore, two general types of rupture disks have been used, namely, the so-called "conventional" disk which includes a concave-convex dome portion positioned whereby fluid pressure from the vessel or system being protected is exerted on the concave side of the dome portion placing the disk in tension, and the so-called "reverse buckling" disk which also includes a concave-convex dome portion, but which is positioned with respect to the vessel or system being protected so that fluid pressure is exerted on the convex side of the dome portion placing the disk in compression. In both conventional and reverse buckling rupture disks, scores have been utilized for creating lines of weakness therein so that upon rupture, the disks tear along the lines of weakness in a predetermined pattern. As used herein, the term "scores" means elongated grooves or other lines of relative thinness formed in a rupture disk.
While conventional disks are presently being used, they are generally confined to applications where the design rupture pressure of the disk is considerably higher than the level of fluid pressure normally exerted on the disk from the vessel or system being protected. If such conventional disks are utilized in applications where the design rupture pressure of the disk is close to the normal fluid pressure exerted on the disk, premature stress failure of the disk can result. Because reverse buckling rupture disks are placed in compression by the fluid pressure exerted thereon, the pressure at which the disk is designed to rupture can be relatively close to the normal fluid pressure exerted on the disk. Further, reverse buckling rupture disks can withstand pressure fluctuations within the vessel or system over a long period of time without premature failure. However, problems have been encountered in the use of scored reverse buckling rupture disks in that such disks sometimes reverse erratically or reverse but do not tear open. In this event, unless the disks are manufactured in a manner whereby the ratio of tension rupture pressure to reversal rupture pressure is low, the fluid pressure required to rupture the disks in tension after reversal can exceed the design rupture pressure of the disks by a considerable amount creating an extremely dangerous over-pressure condition in the vessels or systems intended to be protected.
The heretofore used methods of manufacturing reverse buckling scored rupture disks have generally included forming concave-convex dome portions in the disks to a specific crown height followed by forming scores on one side of the concave-convex dome portion. The scores are formed by forceably contacting the disks with a sharpened blade so that compressed metal indentations are formed in the disks in a desired pattern. A description of this technique is set forth in U.S. Pat. No. 3,921,556 which is assigned to the assignee of this present invention. The techniques of forming scores by forceable contact with a blade or similar tool leaves much to be desired in that the scores formed are often of non-uniform depths, and because the metal is work-hardened by contact with the score blade, problems are encountered in both the manufacture and use of the rupture disks produced. Further, for a particular score blade, only disks of a specific crown height can be scored decreasing the flexibility in design of the disks and increasing the number of steps required to manufacture a group of such rupture disks to design specifications.
By the present invention, an improved method of manufacturing scored rupture disks, both conventional and reverse buckling types, is provided which is economical to carry out as compared to heretofore used manufacturing methods and which obviates the problems mentioned above. Further, the improved method of manufacturing scored reverse buckling rupture disks of the present invention allows greater flexibility in the design of such disks without sacrificing accuracy or efficiency.